[TSDB] Display the current write index when timeseries mode is enabled

[agithomas]

Scenario : Below situation is applicable when TSDB is enabled for a datastream. There exist a scenario when documents will go the old index.

Detailed description : When mappings are modified for a datastream, index rollover happens and a new index is created under the datastream. Even if there exist a new index, the data continue to go to the old index until the timestamp matches index.time_series.start_time.

Requirement : Please show in the UI (please refer below), the current write index.

Benefits Understanding the current write index may become very important when it comes to debugging. If this feature does not exist, It takes a huge amount of time, comparing the value of index.time_series.end_time with current timestamps and timezones . The situation may becomes really difficult if there exist more than one backing index in future having different index.time_series.start_time.

[agithomas]

This mitigates confusions such as this issue mentioned in the Discuss forum

[elasticmachine]

Pinging @elastic/platform-deployment-management (Team:Deployment Management)